Hot water tank flue construction



D: G. LA RUE 2,874,683 HOT WATER TANK FLUE CONSTRUCTION 7 Feb. 24, 1959 2 Sheets-Sheet 1 Filed Jan. 28, 1 955 INVENTOR.

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longitudinal axis of the shell.

United States Patent HOT WATER TANK FLUE CONSTRUCTION Donald G. I4 Rue, Orinda, Calif., assignor to Kaiser Aluminum & Chemical Corporation, Oakland, Calif., a corporation of Delaware Application JanuaryZS, 1955, Serial No. 484,690

scrum. c1. 122-11 This invention relates to a hot water tank construction. More particularly, it is concerned with providing a novel aluminum flue construction forhot water tanks whereby the overall thermal'efliciency of the tank is improved and its life increased.

In'the conventional construction of hot water tanks of thegas or oil fired type, the substantially cylindrical shell and the flue disposed within the shell are both fabricated from a ferrous metal, usually galvanized steel. The flue is generally located within and substantially'along the It is used to conduct the products of combustionaway from the gas or oil burner, as well as to conduct heat fromthe said products of combustion to the waterin the tank. In water heaters of this type, tank failures have been frequently experienced due to the perforation of the galvanized steel flues caused by the corrosive action of the products of combustion thereon, as well' as corrosion by the stored hot water. To overcome this attack on the flue members, it has been proposed to line or clad the inside flue surfaces with a layer of aluminum metal. Although the aluminum linings act to prevent the perforation of the ferrous metal flues as a result of the action of the corrosive gases thereon and assist in prolonging tank life, ultimate tank failures still occur due to the corrosive action of the water on the ferrous metal tank shell. In order to prevent the corroding of the tank shell, it has been further proposed to utilize one or more sacrificial anodes of a metal which will provide cathodic protection to the ferrous metal shell. 1 These are attached to and disposed within the shell. anodes, usuallyof magnesium metal, will afford satis- The addition of a suitable sacrificial anode or factory ample protection to the ferrous metal shell until I the anode is consumed.- However, the overall cost involved in using such an anode, due to manufacturing costs, Whichinclude labor and materials, considerably increase the total cost of the hot water tank.

Therefore, it is a prirnaryobject" of this invention to provide an improved hot water tank construction which,

It is also an object of this invention to provide a novel flue element which, because of its particular configuration, presents a maximum amount of anodic surface area to the water in the tank.

his a further object of this invention to provide an all aluminum flue for a hot water tank which'has a high thermal efficiency and advantageously serves to efficiently conduct heat from the flue gases to the water in the tank overawideareai 7 1 1 Another object of this invention is to provide an all 2,874,683 Patented Feb. 24,1959

figuration presents a maximum amount of anodic surface area to the water in the tank, while at the same time provides a tortuous path for the flue gases thereby giving increased turbulence'to the flue gases and increasing the heat transfer between these gases and'the water in the tank. It is also an object to provide an improved overall hot water tank construction which can be economically manufactured by the use of standard equipment and welding techniques. 1

These and other objects are accomplished by providing in a hot water tank construction having a ferrous metal shell, the inner surface of which is in contact with the Water, a flue comprised entirely of aluminum; Due to the inherent resistance of aluminum to products of combustion from a flame producing means, such as, a gas or oil burner, failures caused by the corrosive action of the flue gases are greatlyreduced. Since the, outer surface of the main body portion of the aluminum flue is in contact with the water, it will provide cathodic protection to the ferrous shell thereby resulting in increased shell life.

In a preferred embodiment of the invention the main body portion of the flue is provided with radially arranged fins extending a substantial distance inwardly or outwardly of the flue into the path of combustion gases or into the water or a combination of both to increase thesurface areas exposed tothe Water and to the combustion gases. Additionally or alternatively the flue may-be corrugated and/or of a circuitous configuration in order to increase further the surface areas of the flue exposed to the water and combustion gases. This results in increased cathodic protection afforded the ferrous metal shell and, additionally,*in increased turbulence'of the flue gases as they pass through the flue thereby increasing the heat transfer from the flue to the water in the tank. Furthermore, a flue composed entirely of aluminum will substantially increase the thermal efliciency ofthe hot water tank by giving a more rapid transfer of heat through the flue to the water inthe tank. This will result in an improved recovery rate as well as a reduced rate offuel consumption. 7 V .In the'specification and the appended claims the'term aluminum flue is used to designate a metal flue which is' made predominantly of aluminum material and the alloys thereof.

of galvanized steel. 1

Other objects and advantages of the invention will become more apparent from a review of the ensuing detailed description when taken in conjunction with the' appended draWings,wherein:

Figure 1 is an elevational side view of a hot water tank incorporating one form of the instant invention,

with portions broken away at the ends to disclose partiallongitudinal sections;

Figure 2 is a sectionalview of the flue shown in the tank of Figure 1 when taken along lines 2 -4 thereof;

Figure 3 is a partial view of a preferred type of flue construction of the instant invention;

Figure 3A is a sectional view of the flue shown in Figure 3 when taken along lines "3a3a thereof} 7 Figure 4 is a partial' view of an additional form of flue configuration;

Also, the term ferrous metal shell as' used herein, includes a coated ferrous metal shell, such as one Figure 8' is a longitudinal sectional view through a portable water heating device wherein the novel flue of the instant invention-may be used to advantage.

Referring now to the drawings, the novel hot water tank 1 of the instant invention generally comprises a ferrous metal shell 1'; a ferrous metal top head or cover 3, and a ferrous metal bottom head or cover 4 welded or otherwise secured to opposite ends of the shell 1 in a manner well known in the art. An aluminum flue member 2 is disposed within the tank shell 1'. Flue member 2 is secured in any suitable manner for joining.

dissimilar. metals of which there are many well known in. the art,.within the openings 3' and 4 in the top and bottom: members or head covers 3 and 4, respectively. A. suitable combustion producing means, such as gas burner 5,v is also disposed adjacent the bottom of flue 2 in a. manner well known in the art and is connected to. a suitable source. of fuel supply. In Fig. 1 flue member 2 is shown as being disposed concentrically in shell 1' along the vertical axis of the tank 1. Although this is the usual location of the flue member 2 in a hot water tank, the novel flue-of the instant invention can be located in. an-otE-center or other position and still. provide the advantageous features of the instant invention.

As indicatedparticularly in Fig. 1', the main body portion of the flue member 2 is shown as having fluted or corrugated portions 12 which may, if desired, be in the form of a spiral. Furthermore, although the main body portion of the flue need not be corrugated, this embodiment of theinvention contemplates that the flue be corrugated either transversely or parallel to its longitudinal axis. The corrugations serve to provide more surface area on the outside of the flue in contact with the water and the inside of the flue in contact with the products of combustion thereby affording greater cathodic protection to the ferrous metal shell as well as giving increased transfer of heat through the flue to the water in-the tank.

Figures 3 and 3A show a preferred embodiment of the flue member 2. As shown in Figures 3 and 3A and Figures 4 and 4A the flue may be made in the form of an aluminum extrusion. In one embodiment, the inner surface ofthe flue 2 has aluminum fins 6 formed integrally therewith which provide for better transfer of heat from the the gases to the flue walls, and in turn to the waterin. the tank. In another form, the extrusion may. he formed with fins 18. extending outwardly from the flue body. The fins 6 and 18 are shown as being disposed parallel to the longitudinal axis of the flue. In Figure 4, the fins 18 are shown disposed radially outwardly of the body-portion 2 and are extruded integrally with the body 2 in an extrusion process. However, the fins may also be disposed horizontally or spirally both alongthe inner and. outer surface of the flue, or on either surface alone, if desired. Also, itis obvious the either surface alone, if desired. Also, it is obvious that the surface:- of theflue could be corrugated. The advantages of the; formation of internally finned elements are self evident and the. use of extrusion methods in the formation of such flues result in economical constructions not.

possible. with conventional materials.

Figurediscloses a means for securing the flue-2 to the. bottom head or cover 4-by way'of a water-tight joint. An opening 4' is punched in the head or covermember 4- 4 to admit the flue 2, and an annular steel boss 7 is welded to the head 4' adjacent opening 4'1 The end of flue 2 adjacent opening 4" is flared by any suitable method, such as spinning, so as to provide a skirt portion 7' thereon. Skirt portion 7 is brought into contact with the inner periphery of the boss 7. Thereafter, a steel or aluminum nut 8 is screwed onto the threaded outer surfaces 8 of the boss 7. When nut 8 which has a J-shaped cross-section, is in threaded engagement with boss 7, contact pressure betweenthe engaging surfaces of the skirt portion 7- offlue 2 and the inner periphery of boss 7 is maintained. A suitable caulking compound may be used if desired to improve the seal. The flue may be secured to the top cover 3 in a similar fashion.

An alternative means for fastening the flue 2 to the head or cover members 3 and 4 is shown in Figure 6. Here the cover member 4 adjacent the opening 4' is flanged upwardly and the outer surface 14 of the flanged portion threaded. The flue may be extended through the opening 4 of the head 4 to any length and a gland nut 9 screwed tightly on a suitable packing material 10 to provide the water-tight seal.

Although only two means of securing the flue member 2-to the cover members 3 and 4 are disclosed, there are many ways including the welding, of dissimilar metal well known in the prior art for joining a tubular member to a head or cover member in a water-tight seal. Accordingly, the invention is not limited to any particular securing means, those disclosed being by way of example only.

Figure 7 shows a modification of the flue construction wherein the flue member 2 is of a circuitous configuration thereby forming a tortuous path for the flue gases and also exposing more surface area of the flue to the water. The mainbody. portion of flue2, disposed within the tank 1, is formed in a sinuous manner such that the main body portion of the flue consists of one or more curved portions. The top end of the flue may be secured to an opening 15 inthe tank shell 1, as shown in Figure 6, by any suitable Water-tight joint, or the flue may be constructedsuch that its top end will be secured to an opening in the top head 3. In addition to the circuitous configuration, the flue may also have surface corrugations, such as the spiral corrugations 12 depicted in the drawing, or other types of corrugations previously described to further increase the surface area in contact with the water and with the-flue gases and also to further increase the turbulence of the hue gases.

The embodiment shown in Figure8 is-a'further modification of the invention. In Figure 8 is depicted a portable immersiontype-of water heatersuch as may be used by the armed services for heating water in the field. In this figure, the heating unit may be disposed within a suitable container 11 having a bottom 20, such as a galvanized steel container, and may comprise an aluminum-flue 2, a suitable ringrshaped fuel tank 16, and a fuelburner 5. Any suitable means" may beprovided for controlling and feeding the fuel to the burner. Flue 2 may be joined to the inner. surface of thering-shaped fuel tank by a suitable water-tight joint as hereinbefore discussed. The bottomplate 13'for the-tank 16, along with the rest of. the tank 16,-forms a water-tightwell in the center of the ring-shaped fueltank for fuel burner 5. Theflue member 2 may assume any of the configurations described hereinabove so as to'increase the heat transfer from-the flue to the water in the tank and afford increased cathodic protection to the container 11.

It is apparentthat'the water heater construction disclosed in the foregoing description will afford increased life and increasedefliciency'to a hot water tank construction by providing a fluemember which is-- economical to manufacture and ofhigh heat conductive material having 7 a high r'esis'tanceto'thecorrosive action: of the-flue gases It is obvious that many changes or modifications may be made without departing from the scope and spirit thereof, and accordingly, the invention is not limited by what has been disclosed in the foregoing description, but only by the appended claims wherein what is claimed is:

1. In a hot water tank construction the combination of a ferrous metal shell member, the inner surface of which is in contact with the water and at least one end head member, one of said members having an opening therein, a combustion producing means for heating the water in the tank, and a flue for carrying OK the products of combustion from said combustion producing means, said flue being comprised entirely of aluminum and having a main body portion disposed within said shell including an outer surface in contact with the water, means mounting said flue within said shell member, one of the ends of said flue being disposed within the said opening in one of said members and the other end of said flue being located adjacent said combustion producing means, whereby the products of combustion of said combustion producing means may enter and pass through the said fine and the said ferrous metal shell member is protected against the corrosive action of the contents of the tank.

2. A hot water tank construction as set forth in claim 1 wherein the main body portion of the aluminum flue comprises an extruded element having finned portions formed integrally therewith.

3. A hot water tank construction as set forth in claim 1 wherein the body portion of the aluminum line includes fin members extending into the path of travel of the products of combustion.

4. A hot water tank construction as set forth in claim 1 wherein the outer surface of the main body portion of the aluminum flue includes fins projecting outwardly therefrom.

5. A hot water tank construction as set forth in claim 1 wherein the aluminum flue has corrugated portions.

6. A hot water tank construction as set forth in claim 1 wherein the aluminum flue has a main body portion disposed within said tank, said main body portion having a circuitous configuration, thereby forming a tortuous path for the products of combustion.

References Cited in the file of this patent UNITED STATES PATENTS 1,170,834 Lovekin Feb. 8, 1916 2,218,422 Haddock Oct. 15, 1940 2,281,206 Schoen Apr. 28, 1942 2,411,675 Alexander Nov. 26, 1946 2,448,128 Trageser Aug. 31, 1948 UNITED STATES PATENT OFFICE CERTIFICATE OF 'CURRECTION Patent Nos. 2,87%683 February 24 1959 Donald G; La Rue It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 66 strike out "either surface alene if desired. Also it is obvious the".

Signed and sealed this 3rd day of January 1961.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of Patents 

